Apparatus and method for controlling valve timing of engine

ABSTRACT

An engine control system has an ECU and a valve timing control device (VVT). The ECU keeps the engine rotation after a driver turns off an ignition switch, and drives the VVT at least a middle position appropriate for starting the engine. Then the ECU stops fuel supply and ignition. Therefore, the VVT is surely driven to the middle position before the engine is stopped. Additionally, the system may shorten an extended running time of the engine since the engine is stopped when the valve timing reaches to the middle position. Further, the engine may be forcedly stopped if the engine is still running when a predetermined time is elapsed after the ignition switch is turned off.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based on Japanese Patent Application No. 2001-88580 filed on Mar. 26, 2001 the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an apparatus and method for controlling valve timing of an internal combustion engine (engine).

[0004] 2. Description of Related Art

[0005] JP-A-7-233713 and JP-A-11-210424 disclose valve timing control apparatus that drives a valve timing actuator to a starting position appropriate for starting the engine when the engine is operated to stop its rotation. The controller disclosed in JP-A-7-233713 keeps to rotate the engine for a predetermined short period of time after a driver operates the engine to stop, and drives the actuator to the starting position while the predetermined time. The controller disclosed in JP-A-11-210424 drives the actuator to the starting position by using residual oil pressure form an ignition switch is turned off.

[0006] However, the prior art cannot ensure that the actuator is driven to the starting position when the engine is completely stopped. Especially, response of the actuator is influenced by condition of the engine such as an oil temperature, an oil grade, and an engine speed when the driver indicates to stop the engine.

SUMMARY OF THE INVENTION

[0007] An object of the present invention is to provide an apparatus for controlling a valve timing of an engine which is capable of controlling the valve timing to the starting position certainly.

[0008] It is another object of the present invention to provide an apparatus for controlling a valve timing of an engine which is capable of controlling the valve timing to the starting position, and shortening an extended running time of the engine after a driver turning off an ignition switch.

[0009] It is further object of the present invention to provide an apparatus for controlling a valve timing of an engine which is capable of controlling the valve timing to the starting position, and preventing a driver from an uncomfortable feeling.

[0010] According to a first aspect of the present invention, the variable valve timing actuator is driven to a specific position where the lock mechanism locks after the engine stopping operation is detected, and the engine is stopped when the variable valve timing actuator reaches to the specific position. The variable valve timing actuator may be driven to a position advanced more than the specific position after the engine stopping operation is detected, and the engine is stopped when the variable valve timing actuator reaches to the advanced position. The variable valve timing actuator is driven to the specific position before the engine is stopped.

[0011] According to another aspect of the present invention, the engine may be stopped when a predetermined time is elapsed from the detection of the engine stopping operation. The predetermined time may be set to be capable of preventing an operator who gives the engine stopping operation from an uncomfortable feeling.

[0012] According to an embodiment of the present invention, the engine stopping operation can be detected by monitoring an ignition switch, and a driver of a vehicle operates the ignition switch. If the engine keeps running after the driver turns off the ignition switch, it seems that the engine is not under control, and the driver may feel uncomfortable. However limiting an engine running time after the ignition switch is turned off can reduce the driver's uncomfortable feeling.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Features and advantages of embodiments will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:

[0014]FIG. 1 is a block diagram of a control system for a valve timing control apparatus according to a first embodiment of the present invention;

[0015]FIG. 2 is a sectional view of a variable valve timing actuator (VVT) according to the first embodiment of the present invention;

[0016]FIG. 3 is a block diagram of the control system according to the first embodiment of the present invention;

[0017]FIGS. 4A, 4B and 4C are schematic sectional view of the VVT showing a lock mechanism according to the first embodiment of the present invention;

[0018]FIGS. 5A, 5B and 5C are schematic sectional view of the VVT showing the lock mechanism according to the first embodiment of the present invention;

[0019]FIG. 6 is a circuit diagram showing a power circuit controlled by an ECU according to the first embodiment of the present invention;

[0020]FIG. 7 is a flowchart executed by the ECU according to the first embodiment of the present invention;

[0021]FIG. 8 is a flowchart executed by the ECU according to the first embodiment of the present invention;

[0022]FIG. 9 is a flowchart executed by the ECU according to a second embodiment of the present invention;

[0023]FIGS. 10A, 10B and 10C are time chart showing an engine speed, a valve timing, and a control signal respectively according to the second embodiment of the present invention; and

[0024]FIG. 11 is a flowchart executed by the ECU according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] In a first embodiment, the present invention is applied to a vehicular engine control system having a variable valve timing control apparatus. The apparatus controls a hydraulic variable valve timing actuator (VVT) to obtain adequate valve timing in accordance with operating condition of the engine.

[0026] Referring to FIG. 1, the engine 1 has a four-cylinder inline layout and is a double overhead camshaft type engine. The engine 1 has an exhaust system that has exhaust manifolds 41 and 43, collector pipes 51 and 52, and a single exhaust pipe 57. The exhaust manifolds 41 meet in the collector pipe 51. The exhaust manifolds 43 meet in the collector pipe 52. The engine 11 has an intake system that has a intake pipe 63, and an intake manifold 61. An airflow meter 21 for detecting an amount of intake air is disposed in the intake pipe 63. A throttle valve 17 for varying the amount of intake air is disposed in the intake pipe 63. Fuel injectors 71 are disposed on the intake manifold 61 corresponding to the cylinders. Spark plugs 81 are disposed on the cylinders respectively. An ignition device having a distributor 82 and an igniter 83 are mounted on the engine 1 and supply high-tension voltage to the spark plugs 81 for igniting air/fuel mixture in combustion chambers la. The engine 1 has a variable valve timing device 10 on an axial end of an intake camshaft. The system has an electronic control unit (ECU) 30 for controlling the injectors 71, the igniter 83 and the variable valve timing device 10. The ECU 30 is a controller. The variable valve timing device may be disposed on at least one of the intake camshaft and an exhaust camshaft.

[0027] FIGS. 2-5 show the variable valve timing device 10. The variable valve timing device 10 has a hydraulic variable valve timing actuator (VVT) 100, and a hydraulic control device for controlling the VVT 100. The hydraulic control device has an oil control valve (OCV) 25 and an oil switching valve (OSV) 240. The variable valve timing device 10 and the ECU 30 provide a variable valve timing controlling system 2 as shown in FIG. 3. FIG. 2 shows a vertical cross-section of the VVT 100. FIG. 3 shows a longitudinal cross-section of the VVT 100. The VVT 100 is disposed on an end of an intake camshaft 11 for driving intake valves. The VVT 100 has a pulley 13, a spacer 101, an end cover 102 and a rotor 110. The pulley 13, the spacer 101 and the end cover 102 are tightened by a bolt 105 to form a housing for providing at least one chamber therein and for accommodating the rotor 110. The housing is rotatably supported on the intake camshaft 11. The rotor 110 is fixed on the camshaft 11 by a bolt 104. The spacer 101 has a cylindrical portion and four shoe portions 103 for providing four fan-shaped chambers. The rotor 110 has a boss and four radially protruded vanes 111. Each vane 111 divides the chamber into an advancing chamber 121 and a retarding chamber 123. A plurality of seal members 107 and 113 are disposed in radial clearances between the spacer 101 and the rotor 110.

[0028] According to the above-described arrangement, the rotor 110 relatively rotates to the housing from a most retarded position to a most advanced position. The VVT 100 is fixed on the camshaft 11 so that a specific position of the rotor 110 corresponds to a starting position that provides the valve timing appropriate for the engine starting. In this embodiment the VVT 100 varies the valve timing over a predetermined movable range. The specific position is located between the most retarded and advanced positions as a middle position. The middle position is located on a retarded side to the center of the predetermined movable range. The middle position is not on the most retarded position. The VVT 100 has a lock mechanism 200 for restricting relative rotation of the rotor 110 by interconnecting the rotor 110 and the housing. The lock mechanism 200 has a lock pin 250 slidably disposed in a circumferentially widest vane 111.

[0029] FIGS. 4A-4C and 5A-5B are schematically cross-sectional views of the VVT to show the lock mechanism 200. The vane 111 has a guiding hole 259 defined by a larger hole 259 a and a smaller hole 259 b. The lock pin 250 has a columnar body 250 b slidably disposed in the smaller hole 259 b and a flange 250 a slidably disposed in the larger hole 259 a. The flange 250 a divides the larger hole 259 a into a control chamber and a back chamber. A spring 257 is disposed in the back chamber for urging the lock pin 250 toward a protruding position, the lock position. The lock pin 250 is axially movable between a lock position and an unlock position in response to an oil supply. The pulley 13 has a circular lock hole 231 and an arc shaped groove 251. The lock pin 250 has a top end that is capable of engaging within the lock hole 231 and is capable of being guided by the groove 251. The lock hole 231 is disposed on the middle position that is defined to improve starting the engine. The groove 251 is formed from the lock hole 231 to an advanced position advanced more than the lock hole 231 but does not reach to the most advanced position. The groove 251 is shallower than the lock hole 231. The lock pin 250 and the groove 251 provides a restricting mechanism for restricting a rotation of the rotor 110 within a range from the middle position to the advanced position defined by the groove 251.

[0030] The lock pin 250 is housed in the vane 111 when oil is supplied into the control chamber to push the lock pin 250 against the spring 257 as shown in FIGS. 4A and 5A. The lock pin 250 engages with the lock hole 231 when the oil is drained from the control chamber to protrude the lock pin 250 from the vane 111 as shown in FIGS. 4C and 5C. The lock pin 250 completely restricts relative rotation of the rotor 110 to the housing and the camshaft 11 at the middle position that provides a starting valve timing appropriate for the engine starting. The lock pin 250 engages with the groove 251 when the oil is drained from the control chamber to protrude the lock pin 250 from the vane 111 as shown in FIGS. 4B and 5B. The lock pin 250 restricts relative rotation of the rotor 110 within a specific range from the middle position to the advanced position.

[0031] Alternatively, components of the lock mechanism may be arranged on the other location. For example, the lock hole 231 and the groove 251 provided as a position determining member may be located on the end cover 102. Further, the lock pin 250 provided as a lock member may be disposed in the pulley 13, and the lock hole 231 and the groove 251 may be formed on the rotor 11.

[0032] The camshaft 11 provides oil passages for supplying operating oil into the chambers formed in the VVT 110. The camshaft 11 has an oil passage 115 for supplying oil to the advancing chamber 121 through grooves 115 a, 115 b and delivery passages 115 c formed in the rotor 110. The camshaft 11 also has an oil passage 117 a for supplying oil to the retarding chamber 123 through a circumferential groove 117 b, radial passages 117 c and openings 117 c formed in the pulley 13. The camshaft 11 and the vane 110 also provides a control passage 241 for supplying and draining oil in the control chamber for the lock pin 250 as shown in FIGS. 5A-5C.

[0033] The OCV 25 is a spool type duty electromagnetic control valve having a valve part and an electromagnetic actuator part 25 b. The OCV 25 has a spool 26 operated by the electro magnetic actuator part 25 b. The spool 26 selectively connects ports 26 a and 26 b with a supply port 26 c or drain ports 26 d and 26 e. The supply port 26 c is connected to a pump 28 driven by the engine 1. The port 26 a is connected with the passage 115 via a cam journal. The port 26 b is connected with the passage 117 a via a cam journal.

[0034] The VVT 100 is advanced when the OCV 25 connects the port 26 a with the port 26 c and connects the port 26 b with the port 26 e. Contrary, the VVT 100 retards when the OCV 25 connects the port 26 a with the port 26 d and connects the port 26 b with the port 26 c. For instance, if 100% duty signal is supplied to the OCV 25, the VVT 100 advances the valve timing. Contrary, if 0% duty signal is supplied to the OCV 25, the VVT 100 retards the valve timing. Therefore, the OCV 25 controls amount and pressure of oil supplied in the chambers 121 and 123 in accordance with a control signal duty. The OSV 240 is an electromagnetic control valve for connecting the passage 241 with the pump 28 or a drain selectively. For instance, the lock pin 250 is retracted when the OSV 240 is turned on to supply oil to the control chamber. Contrary, the lock pin 250 protrudes into the groove 251 and the lock hole 231 when the OSV 240 is turned off.

[0035] Referring to FIG. 3, the ECU 30 is constructed as a microcomputer having a data bus 31, a ROM 32, a RAM 33, a CPU 34, and input and output ports 35 and 36. The ECU 30 is connected with the injectors 71 via a driver. The ECU 30 is operatively connected with the spark plugs 81 via a driver. The ECU 30 supplies duty control signal to the OCV 25 via a driver 25 a. The ECU 30 supplies control signal to the OSV 240 via a driver 240 a. The ECU 30 inputs sensor signals such as an amount of air G detected by the airflow meter 21 and an oil temperature To detected by an oil temperature sensor 70 through AD converter 29. The oil temperature To may be estimated in accordance with a temperature Tw of engine coolant water. The ECU 30 inputs a sensor signal CN1 indicative of a reference rotational position of a camshaft 11 detected by a cam angle sensor 44. The ECU 30 also inputs a sensor signal N1 indicative of a reference rotational position of a crankshaft, and a sensor signal NE indicative of an engine speed both detected by the crank angle sensor 45. Further, the ECU 30 inputs switching signal from an ignition switch 91 and other sensors.

[0036] Referring to FIG. 6, the ECU 30 has at least a battery terminal directly connected with a battery BATT, a +B terminal connected with the battery BATT via a relay 93, and a relay control output terminal connected with relays 92 and 93. The relay 92 is disposed on a power supply line for the igniter (ignition coil) 83, the injectors 71, a generator 96, an air conditioner 97 and the like. The relay 93 is disposed on a power supply line for the ECU 30, the airflow meter 21, an idling speed control valve 18, a vacuum switching valve for a fuel vapor control system and the like. Therefore, the ECU 30 can control the power supply for components of an engine control system.

[0037] The ECU 30 detects an actual valve timing by calculating a difference between the signals N1 and CN1. The ECU 30 defines a target valve timing based on an engine load parameters such as the engine speed NE and an intake air amount G/NE that indicates an amount of intake air per one cycle of the engine rotation. For instance, the ECU 30 looks up a map stored in the ROM 32 for determining the target valve timing. Then the ECU 30 determines a duty value of the control signal for the OCV 25 to drive the VVT 100 to a position where the target valve timing is obtained. Further, the ECU 30 controls the lock mechanism 200 via the OSV 240. The ECU 30 drives the VVT 100 to a retarded position when the engine 1 is in an idling condition. The driver always turns off the ignition switch 91 when the engine 1 is in the idling. Therefore, if the ignition switch 91 is turned off, the VVT 100 should be driven in an advance direction. During the idling, the ECU 30 turns on the OSV 240 to keep the lock pin 250 in the vane 111.

[0038] The ECU 30 turns off the OSV 240 when the engine 1 is driven by a starter motor. During a starting operation of the engine, the lock pin 250 is urged to protrude from the vane 111 by the spring 257, and the pump 28 only provides a small amount of oil due to a very low engine speed. The VVT 100 is rotated in a clockwise direction shown in FIG. 2, therefore, the rotor 110 rotates toward a retard direction. Therefore, if the rotor is in an advance side relative to the middle position, the rotor 110 rotates in a retard direction and the lock pin 250 automatically engages with the lock hole 231. As a result, the VVT 100 provides the starting valve timing during the engine is driven by the starter motor. After the engine 1 begins self-rotation, the ECU 30 maintains turning off the OSV 240 for a specific period of time to stabilize the engine rotation. The ECU 30 detects that the engine 1 reaches a stable rotation, then, turns on the OSV 240 to unlock the rotor 110.

[0039] In this embodiment, the ECU 30 determines that whether or not the oil temperature To increases a predetermined temperature. The oil temperature To is indicative of a stable oil supply. If the ECU 30 detects the predetermined oil temperature, the ECU 30 turns on the OSV 240 to retract the lock pin 250 into the vane 111. As a result, the rotor 110 is released under a restriction, and a rotational position of the rotor 110 is controlled by the ECU 30 to provide the target valve timing as described above.

[0040] The ECU 30 provides a preparation control for next starting operation of the engine 1 when the engine 1 is operated to be stopped. In this embodiment, the ECU 30 drives the VVT 100 to the middle position or more advanced position. As a result, it is possible to provide the starting valve timing in the next starting operation of the engine. Generally, the preparation control comprises the steps of detecting an engine stopping operation by an operator of the engine 1, e.g. the driver on the vehicle, maintaining the engine rotation, operating the variable valve timing device 10 to drive the VVT 100 to the middle position or an advanced position relative to the middle position, and stopping the engine rotation.

[0041] The preparation control is provided by executing a program as shown in FIGS. 7 and B. FIG. 7 shows a main routine for detecting the stopping operation of the driver and controlling the VVT 100. FIG. 8 shows a middle position control routine including an advance control and an engine stop control. In a step 501, the ECU 30 detects turning off of the ignition switch 91 as the engine stopping operation of the driver. If the ignition switch 91 is turned off, the ECU 30 proceeds to a step 502. In a step 502, the ECU 30 executes the routine shown in FIG. 8. In a step 601, the ECU 30 turns off the OSV 240, and outputs the control signal with 75% duty to the OCV 25. Therefore, the OCV 25 supplies oil into the advancing chamber 121 and the rotor 110 rotates in an advancing direction. Alternatively, the ECU 100 may outputs the control signal with 100% duty. In a step 602, the ECU 30 determines that whether or not the actual valve timing Va reaches at least the valve timing Vm that corresponds to the middle position. During the advancing control provided by the steps 601 and 602, the lock pin 250 engages with the lock hole 231 or the groove 251. The groove 251 is effective to catch the lock pin 250 and prevent the lock pin 250 from excess rotation in the advance direction. For instance, the groove 251 may catch the lock pin 250 even if an advancing speed of the rotor 110 is too high. The groove 251 shortens a delay time for engaging the lock pin 250 with the lock hole 231 when the engine 1 is started.

[0042] If the valve timing Va is advanced more than the valve timing Vm, the routine proceeds to a step 603. In the step 603, the ECU 30 stops fuel supply and ignition to make the engine stop. If it is detected that the engine speed NE reaches to 0 r.p.m in a step 604, the ECU 30 turns off the relays 92 and 93 in a step 605. During the engine speed NE approaches to 0 r.p.m, the ECU 30 continuously outputs the control signal to the OCV 25. Therefore, the rotor 110 is maintained in the middle position or in the groove 251. The ECU 30 may stop only fuel supply instead.

[0043]FIGS. 10A, 10B and 10C show behaviors of the engine speed NE, the actual valve timing Va and the control signal respectively under the control of the embodiment. The ignition switch 91 is turned off at t1. Then, the control signal is held at 75% duty. The valve timing Va gradually advances and reaches to the middle position Vm at t2. The engine speed NE is gradually decreased due to stopping the fuel injection and the ignition in the step 603. During the engine speed NE is decreased, the valve timing Va is fluctuated due to a lowering engine speed and lowering oil pressure. Then, the engine speed NE reaches to 0 r.p.m., and the control signal is turned off.

[0044] According to the embodiment described above, the engine 1 may stop earlier than the predetermined time Tm if the VVT 100 reaches at least the middle position. Therefore, it is possible to shorten an engine running time after the driver operate the ignition switch 91. It is possible to lock the VVT 100 in the middle position certainly.

[0045]FIG. 9 shows an alternative embodiment of the present invention. FIG. 9 is an alternative routine for the step 601. In this embodiment, the ECU 30 controls the actual valve timing Va by using a feedback control method such as a PID feedback control. In a step 701, the ECU 30 determines a target valve timing. In this embodiment, the target valve timing is set within a range of the groove 251. Preferably, the target valve timing is set on a position that is slightly advanced side from the middle position. In a step 702, the ECU 30 controls the VVT 100 by the feedback control method. As a result, the actual valve timing Va is maintained within the range of the groove 251. Alternatively, the ECU 30 may output the control signal with 100% duty instead of 75% or feedback controlled value.

[0046]FIG. 11 shows an override timer control for turning off the relays 92 and 93 if the middle position control is held for a predetermined time Tm. According to an embodiment utilizing the routine of FIG. 11, the preparation control further comprises a step of delaying the engine stop at least a predetermined time that is enough to complete the steps 601 and 602 and is also limited to prevent the driver from an uncomfortable feeling.

[0047] In a step 801, the ECU 30 determines that whether or not the middle position control, the step 502, is executed. If the middle position control is executed, the ECU 30 determines that whether or not a timer reaches to a predetermined time Tm. The timer runs during the step 502 is executed, and indicates an elapsed time from the ignition switch 91 is turned off. If the timer reaches to the predetermined time Tm, the ECU 30 turns off the relays 92 and 93 in a manner to override the middle position control. As a result, if the relays 92 and 93 are still turned on due to the determination of the steps 602 and 604 when the timer reaches to the time Tm, the relays are forcedly turned off regardless of position of the VVT 100. For example, the predetermined time Tm is set 0.5 seconds.

[0048] In the embodiment, the engine 1 is kept running after the ignition switch 91 is turned off. The driver who operate the ignition switch 91 may feel an uncomfortable feeling since it seems that the engine 1 doesn't response to the driver's operation or the engine 1 is not under controlled. However, the ECU 30 limits an engine running time after the ignition switch 91 is turned off up to the predetermined time Tm. Therefore, an extended running time of the engine 1 doesn't make the driver uncomfortable. In this embodiment, the engine stop is delayed until the valve timing Va is advanced to at least the middle position or an elapsed time from the ignition switch 91 is turned off reaches to the predetermined time Tm. It is possible to reduce an uncomfortable feeling of the driver, since the engine running time after turning off the ignition switch 91 is limited within the predetermined time Tm.

[0049] Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the present invention as defined in the appended claims. 

What is claimed is:
 1. An apparatus for controlling valve timing of an engine for controlling a variable valve timing actuator that has a lock mechanism to lock the variable valve timing actuator in a specific position appropriate for starting the engine, comprising: means for detecting an engine stopping operation; means for driving the variable valve timing actuator to the specific position or a position advanced more than the specific position after the engine stopping operation is detected; and means for stopping the engine when the variable valve timing actuator reaches to the specific position or the position advanced more than the specific position.
 2. The apparatus for controlling valve timing of the engine according to claim 1, wherein the engine has a fuel injector and an ignition device, and wherein the stopping means stops at least a fuel injection from the fuel injector.
 3. The apparatus for controlling valve timing of the engine according to claim 1 further comprising means for stopping the engine when a predetermined time is elapsed from the detection of the engine stopping operation, the predetermined time being set to be capable of preventing an operator who gives the engine stopping operation from an uncomfortable feeling.
 4. The apparatus for controlling valve timing of the engine according to claim 1, wherein the variable valve timing actuator is hydraulically driven by oil supplied by the engine and is controlled by a hydraulic control device.
 5. The apparatus for controlling valve timing of the engine according to claim 1, wherein the engine stopping means stops the engine when the lock mechanism locks the variable valve timing actuator.
 6. The apparatus for controlling valve timing of the engine according to claim 2, wherein the detecting means includes an ignition switch, and wherein the apparatus further comprises means for providing an electrical connection between the ignition switch and the fuel injector.
 7. The apparatus for controlling valve timing of the engine according to claim 6, further comprising means for providing an electrical connection between the ignition switch and the ignition device.
 8. The apparatus for controlling valve timing of the engine according to claim 1, further comprising means for urging the lock mechanism toward a lock position when the variable valve timing actuator is driven toward the specific position.
 9. The apparatus for controlling valve timing of the engine according to claim 1, wherein the variable valve timing actuator has a restricting mechanism for restricting the variable valve timing actuator within a range from the specific position to an advanced position, the advanced position being defined on an advanced side of the specific position and on a retarded side of a most advanced position.
 10. The apparatus for controlling valve timing of the engine according to claim 1, wherein the variable valve timing actuator has a rotor and a housing relatively rotatable each other, and wherein the lock mechanism has a lock pin urged to a lock position by a spring, a lock hole arranged to engage with the lock pin when the variable valve timing actuator is in the specific position, and a groove arranged to engage with the lock pin to restrict a relative rotation of the rotor within a range from the specific position to the position advanced more than the specific position.
 11. An apparatus for controlling valve timing of an engine for controlling a variable valve timing actuator that has a lock mechanism to lock the variable valve timing actuator in a specific position appropriate for starting the engine, comprising: means for detecting an engine stopping operation; means for keeping the engine running after the engine stopping operation is detected until a predetermined time is elapsed from the detection of the engine stopping operation; means for advancing the variable valve timing actuator toward the specific position after the engine stopping operation is detected; and means for stopping the engine when the variable valve timing actuator is advanced to at least the specific position.
 12. The apparatus for controlling valve timing of the engine according to claim 11, further comprising means for urging the lock mechanism toward a lock position after the engine stopping operation is detected until the engine is started again.
 13. The apparatus for controlling valve timing of the engine according to claim 11, further comprising means for urging the lock mechanism toward a lock position when the engine is driven by a starter motor.
 14. A method for controlling valve timing of an engine having a variable valve timing actuator that has a lock mechanism to lock the variable valve timing actuator in a specific position appropriate for starting the engine, comprising the steps of: detecting an engine stopping operation; driving the variable valve timing actuator to the specific position or a position advanced more than the specific position after the engine stopping operation is detected; and stopping the engine when the variable valve timing actuator reaches to the specific position or the position advanced more than the specific position.
 15. The method for controlling valve timing of the engine according to claim 14, wherein the engine is stopped by stopping at least a fuel injection from a fuel injector.
 16. The method for controlling valve timing of the engine according to claim 14, further comprising a step of stopping the engine when a predetermined time is elapsed from the detection of the engine stopping operation, the predetermined time being set to be capable of preventing an operator who gives the engine stopping operation from an uncomfortable feeling.
 17. The method for controlling valve timing of the engine according to claim 14, wherein the variable valve timing actuator is hydraulically driven by oil supplied by the engine and is controlled by a hydraulic control device.
 18. The method for controlling valve timing of the engine according to claim 14, wherein the engine is stopped when the lock mechanism locks the variable valve timing actuator.
 19. The method for controlling valve timing of the engine according to claim 15, further comprising a step of disconnecting an electrical connection between a battery and a fuel injector.
 20. The method for controlling valve timing of the engine according to claim 19, further comprising a step of disconnecting an electrical connection between a battery and an ignition device. 